A Cyclohexane Multi-solvent System Based On Electrocatalytic Oxidation And Its Influence Law

Selective oxidation of cyclohexane to cyclohexanol and cyclohexanone?KA oil?is one of the most important reactions for the industrial value and the vast demand of feedstock.However,it is also a great challenge in the chemical industry due to the intrinsic inertness of C-H bond.On the base of electrocatalytic membrane reactor for cyclohexane oxidation,a cyclohexane-water-solvent ternary solvent system was constructed to explore the influence of solvent system on the catalytic oxidation of cyclohexane,which is of great significance for KA-oil production.In this paper,the nano-V2O5 catalysts were loaded on the porous Ti membrane to obtain nano-V2O5/Ti membrane electrodes,which can be used as the anode in the electrocatalytic membrane reactor?ECMR?for efficient and selective oxidation of CHA.Field-emission scanning electron microscopy?FESEM?,X-ray diffraction?XRD?,cyclic voltammograms?CV?,electrochemical impedance spectroscopy?EIS?and electron spin resonance?ESR?were used to characterize the catalyst.Results showed that the nanosheet V2O5/Ti membrane electrode with 20-40 nm in thickness and 0.78 wt%loading was prepared by sol-gel method.Obviously,the key points include solvent system except the porous substrate and catalysts.A cyclohexane-water-solvent ternary solvent system was constructed to explore the effect of solvent system on the catalytic oxidation of cyclohexane.According to the principle of similar compatibility,the phase diagram of cyclohexane-water-solvent?acetone/acetic acid?was obtained by turbidity titration to explore the relationship between the solvent characteristics and the solubility of cyclohexane and the catalytic oxidation of cyclohexane.15.5%conversion of cyclohexane and the 99%selectivity to KA oil was obtained under the conditions:the initial concentration of cyclohexane 20 mmol L^-1,the reaction temperature 30?,the residence time 30 min and the current density 3.0 mA cm-2.Interestingly,K/A value was up to 8.9,which demonstrated that more produced A had been further oxidized to K.The optimization of response surface methodology showed that cyclohexane conversion was up to 16.8%and selectivity to K was 90.2%,under the operating conditions:cyclohexane initial concentration was 20.00 mmol L^-1,temperature 26.54?,current density 46 mAcm-2,residence time 30.77 min.In addition,the significant order of the factors influencing the conversion of cyclohexane followed:current density>concentration>residence time>temperature;the order of importance of the factors influencing K selectivity as residence time>current density>concentration>temperature.Furthermore,the between residence time and concentration were more significant than the others.The effect of solvent system on product selectivity,is mainly related to the solubility of products in the solvent.Among KA oil,K is more easily desorbed from the catalyst surface,so cyclohexanol is further oxidized to cyclohexanone,leading to high cyclohexanone selectivity.Moreover,a five-stage fixed bed membrane reactor was designed and used to achieve continuous catalytic oxidation of cyclohexane?residence time 10 min,flow rate 0.6 mL min-1?with a flat V2O5/Ti electrode?50 mm in diameter,2,60 mm in thickness and 22.25%porosity?.The results showed that cyclohexane conversion reached 8.2%when cyclohexane concentration was 240 mmol L^-1.